Switch



Oct 1939- N. c. SCHELLENGER 7,

SWITCH Original Filed June 6, 1936 F 2 3 102 S Q 1/2 92 1042 a 16 a INVENTOR. NGHJZO/Z fificfzdlar er;

ATTORNEYS Patented Oct. 24, 1939 UNITED STATES PATENT OFFICE SWITCH Original application June 6, 1936, Serial No.

83,963. Divided and this application April 27,

1939, Serial No. 270,281

7 Claims. (01. 201-55) This invention relates to a new and improved construction of a combined variable resistance and switch and more particularly to such a combination in which the switch is electrically shield- 15 ed from the variable resistance.

This application is a division of my copending application Serial No. 83,963, filed June 6, 1936, and a continuation as to all common subject matter of my copending application, Serial No.

10 54,407, filed December 14, 1935.

- While my improved switch and variable resistance combination may be used for controlling any electrical circuits which do not exceed the power carrying capacity of the switch it is 15 especially adapted for use with radio sets to control the current supplied to the set.

My improved construction is particularly adaptable for use in automobile radio sets which are designed and manufactured to have a very high 29 sensitivity which is required by the comparatively small antennaes with which they are operated. Recently because of the use of the so-called turret top or one-piece metal top on automobiles, the antennaes have been placed under the car 25 or under the running board where they are smaller than those formerly used in car tops, and also are less effective due to closer proximity to ground. For these reasons automobile radios are now made with an even higher degree of sensitivity.

The highly sensitive automobile radio must be shielded from the high frequency disturbances set up by the ignition system of the automobile. Since the ignition system and the radio are operated from the same battery, these disturbances must be prevented from reaching the sensitive set circuits through the power supply lines. An even more important factor in automobile radios and also a factor in certain types of home radios which are now designed to operate entirely from 40 a six volt battery is the interference created by the vibrator type of high voltage supply for the radio set. This type of high voltage supply includes a vibrator which breaks up the six volt primary of a step-up transformer into a very 45 rough wave form which is also, of course, present in the high voltage secondary circuit. The switch which controls the current supply to the heaters or filaments of the tubes controls the six volt supply to the vibrator and as a result, any 50 resistance in series with these two circuits will cause a voltage drop due to each component. The voltage drop due to the vibrator component will have the same wave form as the current and will be impressed upon the leads going into the 5 heaters or filaments of the tubes and will thus convey interference into the set. This effect can be minimized or substantially eliminated by the use of a low resistance switch. This rough wave form will further cause an electrostatic transfer from the switch to the volume control unless adequate shielding between them is provided.

With many types of combination switches and variable resistances now in use, the switch cam is formed of metal and is insulated both from ground and from the current carrying portions of the switch when the switch is in the closed position. While shielding is interposed between the current carrying portions of the switch and the resistance, there is none interposed between the current carrying portion of the switch and the cam and none between the cam and the variable resistance. This means that the metal cam structure can act as a transfer agent from the switch enclosure to the volume control enclosure by the process of re-radiation, minimizing to a certain extent the efiectiveness of the switch shield.

It is an object of the present invention to provide a new and improved switch construction.

It is a further object to provide a shield construction in combination with such a switch.

It is another object to provide a switch construction in which the switch operating cam serves as 'a' portion of the shield between the switch and variable resistance.

It is an additional object to provide a switch composed of but few and simple parts and adapted? for easy assembly.

/ It is another object to provide a switch which is comparatively inexpensive to manufacture and adapted for commercial production and use.

Other and further objects will appear as the description proceeds.

I have shown certain preferred embodiments of my invention in the accompanying drawing, in which- Figure 1 is a view in elevation showing the improved switch applied to a variable resistance;

Figure 2 is a-view of the combination of Figure 1 on a somewhat larger scale and taken substantially on line 2-2 of Figure 1, with the housing members in section, the variable resistance shield disc partly in section, and the remaining parts shown in elevation;

Figure 3 is a section of the combination device of Figure 2 taken substantially on line 3-3 of Figure 2;

Figure 4 is a plan view of the switch housing assembly shown in Figure 1; and

ating member.

Referring to the drawing, the variable resistance unit is provided with the housing I8, which supports the switch housing I2. The housing I0 is a cup-shaped member having a top portion I4 which serves as a fixed metallic shield between the switch and the variable resistance. The switch housing I2 is provided with a plurality of cars l6 which extend through elongated perforations in the top portion I4 of the housing I2, and are turned over against the under face of the portion I4 to firmly secure the switch housing in place upon the variable resistance housing.

This connection between the switch housing I2 and variable resistance housing I8 also serves 'to electrically connect the two housings. The intermediate shield portion I4 of the housing I8 is provided with the opening I8 through which the switch cam 28 projects.

The variable resistance device is controlled by the shaft 22 which is journalled in the thimble 24 and carries the disc 26 which is retained on the inner end of the shaft 22 by the swaged inner end 21 of the shaft. The rotating disc carries the switch operating pin 28 which coacts with the switch cam 28.

The base 38 of the variable resistance device is formed of sheet insulating material and the metal shield plate 32 is carried upon its outer face. The flange 34 on the inner end of the thimble 24 engages the inner face of the base 38 and the portion 35 of the thimble retains the washer 36 against the outer face of the plate 32, to retain the base elements in. assembled relation. The assembled unit may be supported on a panel or chassis flange indicated in broken lines 38 on Figure 1 by means of a nut 48, screwed upon the threaded portion 25 of the thimble 24.

As will be seen in Figures 1 to 3 inclusive, the

major portion of the cylindrical flange of the housing I8 extends beyond the edge of the base member 38 and the housing I8 is provided with ears 42 which are bent over against the plate 32 to secure the housing I8 to the base 38. The insulating strip 44 extends around the inner face of the cylindrical wall of housing I8 and serves to space the shield wall I4 at a predetermined distance from the base 38. The base 38 is provided with an extended portion 3| to carry the terminals and the housing I8 is cut away at H as shown in Figures 1 and 3 to clear the extended portion 3| and the terminals. The insulating strip 44 substantially closes the cut away partlon II. The lateral edges of this portion II engage the edges of the extended portion 3| of the base and thus have the function of definitely and permanently locating thehousing I8 and the switch supported thereby, relative to the base.

The arcuate strip 46 carries the fllm or layer of resistance material 41. This strip 46. may be formed of paper, fibre, sheet bakelite or similar material and is secured to the base 38 by the terminals 48 and 49 and the rivets 58 and 5|. The insulating washer 52 fits about the shaft 22 against the inner end of the thimble 24 and carries a collector ring 54 which has a downturned locating lug 55 extending into the notch 53 of washer 52 as shown in Figure 3. The ring 54 is also provided with the connecting extension 58 which passes downwardly through the opening 51 in the base 38. The center terminal 58 is connected to the extension 56 by means of the rivet 88 which passes through the extended portion 3| of the base 38.

Figure 5 is a perspective view of the switch actu- The insulated contactor drive disc 62 is mounted upon shaft 22 below the metallic disc 25 and is provided with a notch 64 into which extends the downturned lug 66 on the disc 28. The interengagement of this lug 68 and notch 64 causes the disc 62 to rotate with the shaft 22 and disc 28. The contact drive arm member 68 is secured to the under side of the disc 62 by means of rivet 68 and engages the collector ring 54. The contactor I8 is provided with the upstanding ears II by means of which it is driven by member 68. The member 88 is provided with an upturned lug I2 which engages in the notch 54 of disc 82 to assist the rivet 69 in properly locating the member 68 relative to disc 62 and shaft 22. The shaft 22 has the groove I3 formed therein to receive the c washer I4 which serves to maintain the parts in assembled relation.

The switch base I6 is held in the switch housing I2 by means of the inturned flange I8 on the outer edge of the housing and by the inturned lugs 88 which engage the inner face of the base. The flange I8 is cutaway at I9 to provide ample clearance between the flange and the terminal 89. The base I8 is notched to engage the inwardly bent portion 82 of the housing I2 as shown in Figures 1 and 2. The flange I8 is extended at 83 to cover this portion 82 (see Figure 4). The indented portion 82 of the housing serves not only as a stop and grounding contact for the switch cam 28 but also serves to positively locate the base I6 relative to the housing I2.

The pivot member 84 is riveted in place in the base I8 and supports the switch cam 28. The fixed contacts 86 and 81 are riveted to the base I6 by means of reduced extended portions 88 and SI which also serve to rivet in place the connecting lugs 88 and 88 on the outer face 'of the base member. The flxed contacts 86 and 81 are cylindrical in form and may be silver plated or otherwise treated to reduce resistance.

The elongated movable contact member I88 is carried between the switch arm 92 and the base 16. This member I88 is of a thickness less than the-height of the fixed contacts 88 and 81 and consequently fits somewhat loosely between the swit J1 arm and base since the switch arm is held away from the base by the fixed contacts.

The switch cam 28 is formed as a unitary metal member which is U-shaped, with an upper leg I28, a lower leg I22 and a connecting portion I24. The lower leg I22 has an opening I23 which fits on the pivot 84 adjacent an enlargement thereon. This portion is also provided with the opening receiving the end of the spring H2. The lower leg I 22 has formed thereon the lugs I28 and I28 which alternately engage the portion 82 of the switch housing I2 so that the switch cam is grounded to the housing in both the on and oil positions of the switch.

The upper leg I8 is provided with an opening I2I which fits on the pivot 84. The openings HI and I23 are in alignment and give the cam 28 a double bearing on the pivot so that it operates freely and without binding.

The switch is comparatively simple in design and in assembly, and efllcient in operation. The housing assembly is important in that it permits the manufacture of a switch of this chm acter without the necessity for the use of any expensive molded housings. The use of the indent 82 in the switch housing I2 permits the formation of a stop without additional material or separate assembly operations, the stop serving both to locate the switch base I8 and to stop and ground the switch cam 20. The fixed contacts are solid members which are simpler to assemble and adjust than spring contacts which are often used for this purpose and which require careful adjustment as to position and resilient thrust.

In the operation of the switch it will be apparent that with the switch in the off position, the portion I29 of the switch cam 20 engages the indented portion 82 of the switch housing, thus not only limiting the movement of the cam but effectively grounding the cam. With the switch in the on position the portion I28 of the cam 20 engages the indented portion 82. The lower leg I22 of the switch cam 20 overlies the opening IS in the housing ID of the variable resistance. The switch pivot 84 and the upper leg I20 of the cam extend through this opening in the housing. This mass of grounded metal overlying the opening and extending through it serves as an effective shield to prevent any electrical coupling, whether electrostatic, electromagnetic or capacitive in character, between the fixed switch contacts and the movable switch contact, all of which are located eccentrically of the opening I8 in the housing. This cam is effectively grounded when the switch is in closed position, at which time the electrical apparatus with which the combination device is associated is in use. Therefore the shielding is fully effective when the device is in use and prevents any transfer of burn or other electrical disturbance from the switch to the variable resistance.

While I have shown certain preferred embodiments of my invention, these are to be understood to be illustrative only, as I contemplate such changes and modifications as'come within the spirit and scope of the appended claims.

I claim:

1. In combination: a variable control unit for use in highly sensitive radio circuits, having a rotatable operating shaft; a metal casing for said variable unit, said casing having end walls; one of which carries a bearing for the rotatable operating shaft; a substantially cup-shaped metal housing having its open end mechanically and electrically connected with the other end wall of said casing; said other end wall of the casing having an aperture therethrough; switch mechanism in said housing including a metal switch actuating cam having a portion closely adjacent to the wall and overlying said aperture to cooperate with the apertured wall for shielding the switch from the control unit; means providing a transient operating connection between the-shaft and the cam for actuation of the switch; and a metal stop on the switch housing engaged by the cam when the switch is closed for grounding the cam to the housing and casing.

2. In a combined switch and control unit for radio circuits of the type wherein a single rotatable shaft operates both the switch and the control unit: a substantially cup-shaped metal casing for the control unit having an aperture through its bottom wall considerably smaller than the total area of said wall; a metal housing for the switch having one open side; means for mechanically and electrically connecting the housing to the bottom wall of the cup-shaped casing so that said wall closes the open side of the housing to electrically shield the switch from the control unit; a metal actuating cam for the switch projecting through said aperture and having a portion overlying the aperture to substantially close the-same; and cooperating means on the cam and the metal switch housing providing a metal to metal contact between the cam and. switch housing to limit the motion of the cam in switch closed position and ground the cam to the connected housing and easing so that the cam coacts with the apertured bottom wall of the casing in shielding the switch from the control unit.

3. In a combined switch and control unit for radio circuits of the type wherein a single rotatable shaft operates both the switch and the control unit: a substantially cup-shaped metal casing for the control unit-having an aperture through its bottom wall considerably smaller than the total area of said wall; a metal housing'for the switch having one open side; means for mechanically and electrically connecting the housing to the bottom wall of the cup-shaped casing so that said wall closes the open side of the housing to electrically shield the switch from the control unit; a metal actuating cam for the switch projecting through said aperture and having a portion overlying theaperture to substantially close the same; an inward integral indentation in the side wall of the switch housing; and an extension on the metal cam engageable with said indentation in the switch closed position to ground the cam to the connected housing and casing so that the cam complements the apertured casing wall'and assures more complete shielding between the switch and the control unit.

4. In a combined switch and control unit for radio circuits of the type wherein a single rotatable shaft operates both the switch and the control unit: a substantially cup-shaped metal casing for the control unit having an aperture through its bottom wall considerably smaller than the total area of said wall; a metal housing for the switch having one open side; means for mechanieally' and electrically connecting the housing to the bottom wall of the cup-shaped casing so that said wall closes the open side of the housing to electrically shield the switch from the control unit; a metal actuating cam for the switch projecting through said aperture and having a portion overlying the aperture to substantially close the same; an inward integral indentation in the side wall of the switch housing; and spaced lugs integral with the cam engageable with opposite sides of the indentation for defining the limits of motion of the cam and for grounding the cam at both of its limits of motion to the connected housing and easing so that the cam complements the apertured casing wall to assure more complete shielding between the-switch and the control unit. i

5. In an electric snap switch of the type adapted to be mounted on the back of the metal casing of another control unit: a metal switch actuating cam having a spring toggle driving connection with the movable part of the switch; a metal housing for the switch; means for mechanically and electrically connecting the housing of the switch with the back of the control casing in a manner projecting part of the actuating cam through an aperture in said back of the'casing whereby the cam is operable from a moving part of the control and whereby the cam complements the apertured back wall of the control casing to insure the optimum electrostatic shielding between the witch and the control; and cooperating mea on the switch housing and the metal cam enga able to define the limits of movement of the cam and to electrically ground the cam to the switch housing at both of its two limits of movement. l

.whereby the cam is operable from a. moving part of the control and whereby the cam complements the apertured back wall of the control'ca'sing to insure the optimum electrostatic shielding between the switch and the control; an inward indentation in the side wall of the switch housing adjacent to the cam; and spaced apart lugs on the cam engageable with opposite sides oi? the indentation for defining the limits of motion of the cam, one or the other of said cam lugs being held in "engagement with said indentation by the spring force on the toggle except when the cam is in motion to trip the switch, so that the cam is normally groundedto the switch housing.

7. In a switch assembly, the combination of a non-conducting base, a snap switch supported by the base, said switch including a non-conducting member carrying a movable contact, a metallic actuating cam and snap mechanism, a metallic shield covering the movable contact and having an opening through which a portion of the cam projects to be engageable by an actuator movable across the shield at the opposite side thereof, said cam having another portion covering a substantial part of the opening in the shield, and metal stop means connected with the shield and positioned to beengaged by and electrically connect the actuating cam at its limits of movement with the shield so that the cam is grounded and coacts with the shield in shielding the switch from any electricalinstrumentality located on the opposite side of the shield.

NEWTON C. SCHELLENGER. 

